Various products, from anti-fog sport goggles, dive masks and other highly portable transparent anti-fog eye-protecting shields, to hand-held GPS devices, radios, telephones and other portable electronics devices having display units, use batteries not only to power these devices but also to heat the devices to prevent fogging of an eye shield or viewing screen. And while some of these devices have commonly used Lithium-Ion batteries to power the devices, the use of Lithium-Ion batteries is not as well known in others, such as the powering of heated eye shields. And yet it would seem desirable to use the benefits of Lithium-Ion battery technology in many more such devices to provide power to provide power to them them, except that a known issue with Lithium-Ion batteries is the fact that, as their charge decreases over time in use, the voltage output they provide also decreases over time in use.
A common characteristic of such portable devices is the fact that they are light weight enough to be carried on a user's body, e.g., worn on a user's head. Examples of fog-prone sport goggles intended for use during winter activities, have included goggles for downhill skiing, cross-country skiing, snowboarding, snowmobiling, sledding, tubing, ice climbing and the like, and are widely known and widely utilized by sports enthusiasts and others whose duties or activities require them to be outside in snowy and other inclement cold weather conditions. Examples of fog-prone dive masks have included eye and nose masks independent of a breathing apparatus as well as full-face masks in which the breathing apparatus is integrated into the mask. Examples of fog-prone eye-protecting shields have included a face shield that a doctor or dentist would wear to prevent pathogens from getting into the user's mouth or eyes, or a transparent face shield portion of a motorcycle helmet. Fogging that impairs vision is a common problem with such goggles, dive masks and eye-protecting shields.
Examples of hand-held devices that require consistent power to heat the displays of such devices to prevent fogging of the display have included hand-held GPS units, radios, telephones, medical devices (EKG readouts), readers, tablets, portable computers, point of sale terminals, etc.
There have been various conductive apparatus devised for preventing condensation build-up on eye-shields and viewing screens of such hand-held devices. The purpose of these conductive apparatus has been to provide an eye shield and viewing screen that may be maintained free of condensation so that the user would be able to enjoy unobstructed vision and viewing during viewing activities. Prior sports goggles and hand-held electronic devices with electronic systems have been primarily used in environments requiring a high degree of portability, that is, where a power source for powering the electronics for the device has been advantageously carried on a strap for the goggle or on the device itself as shown and described in co-pending U.S. Patent Application Ser. No. 61/563,738, by McCulloch, for Modular Anti-fog Goggle System. While such battery-powered devices, especially heating devices which consume extraordinary amounts of power from batteries, need to be judicious in the use of total power source, generally measured in amp-hours, to preserve power source life, it has also become important that the power circuitry of such systems provide a consistent level of power to the device, even though the device battery may become increasingly depleted over time in use. Thus, the ability to adjust the amount of current delivered to the device's resistive element, compensated for decreasing voltage as the battery charge is depleted, has also become desirable.
Thus, while it has remained an important goal to maximize battery life, in which case the use of pulse-width modulation (PWM) has proven useful as described in co-pending U.S. patent application Ser. No. 13/397,691 for PWM Heating System for Eye Shield, Publication No. US-2013-0212765-A1, the limitation of Lithium-Ion battery depletion and correspondent voltage depletion has remained a problem. Thus, it has been recognized that, where there is sufficiently available battery power to perform heating operations on a goggle or hand-held device, an appropriate amount of additionally available power may be useful to make power supplied to the device more consistent throughout the depletion cycle of the battery.
No prior art goggle or hand-held electronic devices have made use of their battery supplies to provide consistent power to the device despite depletion of battery charge. U.S. Pat. No. 4,868,929, to Curcio, for Electrically Heated Ski Goggles, comprises an eye shield with embedded resistive wires operatively connected via a switching device to an external power source pack adapted to produce heating of the eye shield for anti-fog purposes. U.S. Pat. No. 7,648,234, to Welchel et al., for Eyewear With Heating Elements, discloses use of nichrome and thin film heating elements used for heating an eye shield and discloses use of a control mechanism for turning on and off the heat to the eye shield. Neither discusses the foregoing power regulation, conservation and distribution concepts using PWM circuitry to provide more even power to the device despite charge depletion.
A problem with sport goggles which have employed electrical heating is that of uneven heating over the entire surface of the eye shield. Goggles and goggle eye-shields are manufactured with an irregular shape required to maintain a position close to the face of the wearer and allowing cutouts for the nose and extended edges for peripheral vision. Even heating of this irregular shape has not been accomplished in the prior art.
Prior art devices having irregularly-shaped eye shields have been susceptible to hot spots, and using such devices in limited battery-powered applications has unduly discharged the battery. The reason for the hot spots has been because the electrical resistivity between the electrical connections across the resistive elements on the eye shield has been greater or lesser at different locations on the eye shield such that the amount of electrical current consumed in the areas with less distance between terminal connections is greater and the amount of electrical current consumed in areas with greater distance between the terminal connections is less. For example, where the terminals are on either side of the lens in a resistive wiring application, there have been problems with evenly heating the lens since the distance the wire has had to travel from one terminal to the other has been greater for those wires traveling over the bridge of the nose and down under the eyes than other wires that travel the shorter distance across a central portion of the lens. To overcome fogging conditions enough power must be applied to overcome the fog in the areas with the greatest distance between the terminal connection points, causing the smaller areas to overheat, which in turn wastes power. Thus, the problem has resulted in limited usefulness of heating of goggle eye-shields. Because of the irregular shape of eye shields, these problems exist whether one is considering resistive wire applications or resistive-film applications.
Thus there has developed a need to provide a preferably automatically adjusting variable power source which can provide adequate current to meet the requirements of anti-fogging a device, or heating of the device for other reasons, all while providing consistent power despite battery depletion across the load and without presenting excessive power above that which is required. Also there has developed a need to provide multiple current supplies to multiple heating element regions to enable even heating of goggle eye-shields across the entire eye shield surface while providing consistent power despite battery depletion across each region, or load, but without excessive use of power or hot-spots at each region, or load.
Switching the power on to a goggle when you experience fog conditions, and then switching it off when a user suspects it is no longer needed, or doing this to otherwise provide desired heat or power to a hand-held device, is not an efficient way to overcome fog or to otherwise heat or provide power to a device. This is because while the device is on, it is using full power and this is an inefficient use of battery resources. Also, the user doesn't really know precisely when to turn it off, so at best the user is guessing when is the best time to turn it off. Further, when a user is involved and concentrating on the activity at hand, it often is not convenient to have to turn on, or off, the power to heat the eye shield or other hand-held device. Manual switching of power to an eye shield or other hand-held device doesn't allow the user to set an intermediate heat value that is sufficient to curtail fogging or otherwise heat but which also conserves battery life. Further, there are no known systems disclosed in the prior art for balanced heating of a film or other resistive element on an eye shield or hand-held screen, while compensating to provide consistent power despite battery depletion, which also provide variable control of a heating element on the device.